The present invention relates to an Islamic prayer calculator/clock device, and more particularly relates to a calculator/clock device which can calculate the appropriate times for Islamic prayer on an arbitrary date at an arbitrary point on the surface of the Earth, based upon latitude and longitude information relative to said point.
In the Islamic religion it is required to perform acts of prayer five times per day, and it is very important from a religious point of view that these acts of prayer should be performed at or soon after certain predetermined times of day. These correct and appropriate times of day are specified in Holy Writ, or rather methods for calculating them are so specified; and in more recent times elucidations of the precise methods for determining such times have been made by scholars. Various algorithms by which the appropriate prayer times are determined are per se known.
However, the problem has always existed, and has plagued Muslims, that these prayer times, for any particular point on the Earth's surface, are all determined strictly in terms of the position of the Sun in the heavens as seen at that point. For example, one school of scholarship holds that the appropriate time for the starting of the first prayer of the day, or "FAJR", is at the instant that the center of the Sun passes through an imaginary line in the heavens 18.degree. below the eastern horizon line. All the other prayer times are likewise determined in the same way in terms of the position of the Sun in the heavens, as for example the start of "ZOHR" which is considered to be at the instant that the center of the Sun reaches the zenith in the heavens or the highest point above the horizon in that particular day. Now to determine at what times (referred either to Greenwich time or local time) the Sun attains these positions in the heavens, as viewed from a particular point on the Earth's surface, is most difficult without the making of detailed astronomical observations. This has been a matter of concern to religious people in Islam for centuries, because the performance of prayer at the appropriate times is very important for the devout.
A solution which has been practiced in the past is to perform calculations for certain important points on the Earth's surface of the position of the Sun in the heavens, based upon tables and equations of the Earth's rotation and orbital motion around the Sun, and to publish tables of appropriate prayer times. This solution has been appropriate within its limits; however, the shortcomings thereof are: first, that it involves much labor; and, second, that it can only be performed for a certain limited number of important or reference points. For instance, tables are nowadays thus made available of appropriate prayer times only at specific locations in a few major cities. For each country of the world, in fact, tables are available of appropriate prayer times only at certain key points. To a crude approximation, the appropriate prayer times for intermediate points can be obtained by a process of interpolation; but the results obtained are only guesswork, which is from the strict religious point of view quite unacceptable. In principle, even a movement of a few thousand meters on the surface of the Earth makes an appreciable difference to the appropriate times for prayer. Further, the repeated preparation of these tables of prayer times even for a limited number of points continues to cause great labor and uncertainty to the religious community. In the Middle Ages such religious prayer time calculation requirements were the spur to the flowering of Arabic astronomical and mathematical knowledge; but nowadays this motivational advantage is rather obsolete, along with increasing astronomical and scientific sophistication and accuracy in the general scientific world. The problem of calculating these prayer times has been further exacerbated, as the world of Islam has expanded all over the globe.
Algorithms exist nowadays for determining the precise absolute position of the Sun in the heavens at any particular time. Further, corresponding inverse algorithms are currently known for determining at what time on a particular day the Sun will be in a particular absolute heavenly position.
Further, in the past it was not very easy to know the precise location of any arbitrary point on the surface of the Earth. Such determinations could only be made by detailed and difficult astronomical or surveying observations performed at that point. However, recently very accurate maps of various countries prepared by new satellite and radar techniques have become available, indicating with great exactness the latitude and longitude of a great variety of identifiable points. It is not now beyond the ability of any person to precisely known the latitude and longitude of even the most remote and most inaccessible village, and of course this information never changes.
Yet further, in the matter of clocks and calculators relating to Islamic prayer times, it is per se known for an ordinary type of clock to be provided with multiple audible announcing devices or alarms which can be set for indicating the occurrences of the appropriate times for prayer. However, such alarms have in the prior art always been required to be manually set to the proper local prayer times, in accordance with published time tables, and accordingly such art has not contributed in any way to the problem of actually establishing these local prayer times.